A high-barrier polyethylene composite film and its preparation method

Abstract

The present invention discloses a high-barrier polyethylene composite film and a preparation method thereof, which relates to the technical field of polyethylene packaging materials and is made by co-extrusion blow molding of an inner layer, a middle layer and an outer layer; the raw materials of the middle layer include, by weight: 80-120 parts of polyethylene, 10-20 parts of maleic anhydride grafted polyethylene / mica sheet composite material, 10-20 parts of polyolefin-coated modified nanoparticles, 2-6 parts of kaolin / modified nano-aluminum oxide composite material, 3-7 parts of modified cyclodextrin / nano-zinc oxide composite material, and 0.1-0.2 parts of cross-linking agent. The beneficial effect of the present invention is that polyethylene is blended with maleic anhydride grafted polyethylene / mica sheet composite material, polyolefin-coated modified nanoparticles, bentonite / modified nano-aluminum oxide composite material, modified cyclodextrin / nano-zinc oxide composite material and cross-linking agent to form pellets for the middle layer, and then co-extrusion blow molding with the inner layer and the outer layer to make a composite film, which can improve the mechanical strength and barrier properties of the composite film.

Description

Technical Field

[0001] The present invention relates to the technical field of polyethylene packaging materials, and particularly relates to a high-barrier polyethylene composite film and a preparation method thereof. Background Art

[0002] One of the many main uses of polyethylene is film applications, such as food bags, liners for cans in the catering or consumer goods industries, shopping bags, shipping bags, food packaging films, liners for multi-wall bags, product bags, cooked food wrapping materials, tension wrapping materials, and heat-shrinkable wrapping materials. The key physical properties of polyethylene films include tear strength, impact strength, tensile properties, stiffness, and transparency.

[0003] In order to improve the performance of the film, composite films are usually used. A composite film is a combination of two or more materials through one or more composite processes to form a composite material with certain functions. It can generally be divided into a base layer, a functional layer, and a heat-sealing layer. The base layer mainly plays roles such as aesthetics, printing, and moisture barrier. Such as BOPP, BOPET, BOPA, MT, KOP, KPET, etc.; the functional layer mainly plays roles such as barrier, light shielding, etc., such as VMPET, AL, EVOH, PVDC, etc.; the heat-sealing layer is in direct contact with the packaged article and plays functions such as adaptability, permeability resistance, good heat-sealing property, as well as transparency, opening property, etc., such as LDPE, LLDPE, MLLDPE, CPP, VMCPP, EVA, EAA, E-MAA, EMA, EBA, etc.

[0004] In recent years, due to excellent barrier properties, low cost, easy use, good transparency, strong printing adaptability, good mechanical properties and other advantages, high-barrier film materials have been widely used in the packaging of products such as food, medicine, and chemicals in the market, as well as in the fields of electronic device packaging and fuel cell diaphragms, and have developed rapidly. Excellent barrier performance is an important characteristic of high-barrier film materials, including good gas barrier property, moisture barrier property, oil barrier property, fragrance retention property, etc. Early barrier film materials were represented by films such as ethylene-vinyl alcohol copolymer (EVOH), polyamide (PA), polyvinylidene chloride (PVDC), and polyvinyl alcohol (PVA). However, with the strong demand in the fields of food and beverage, medical, chemicals, daily necessities and other products, the requirements for packaging barrier properties have become increasingly strict. For example, for the film prepared by adding ethylene-vinyl alcohol copolymer (EVOH), since the barrier property of EVOH is greatly affected by the environment, when the humidity > 60%, its barrier performance decreases significantly, and it can only be used in a dry environment; for the film prepared by adding polyvinylidene chloride (PVDC), it has the characteristics of flame resistance and corrosion resistance, but polyvinylidene chloride (PVDC) has strong polarity, is insoluble in common solvents at room temperature, has poor light and heat stability, and the film preparation process is difficult; for the film prepared by adding polyvinyl alcohol (PVA), it has poor water resistance, and when it absorbs moisture or water, the films are prone to adhesion and have the effect of water absorption and swelling. Therefore, it is of great significance to develop a polyethylene film with high barrier properties. Summary of the Invention

[0005] An object of the present invention is to solve at least one of the technical problems existing in the prior art, and to provide a high-barrier polyethylene composite film and a preparation method thereof.

[0006] The technical solution of the present invention is as follows:

[0007] A high-barrier polyethylene composite film is made by co-extrusion blowing of an inner layer, a middle layer and an outer layer;

[0008] The raw materials of the middle layer include, by weight: 80-120 parts of polyethylene, 10-20 parts of maleic anhydride grafted polyethylene / mica sheet composite material, 10-20 parts of polyolefin-coated modified nanoparticles, 2-6 parts of kaolin / modified nano-aluminum oxide composite material, 3-7 parts of modified cyclodextrin / nano-zinc oxide composite material, and 0.1-0.2 parts of cross-linking agent.

[0009] A preferred embodiment of the present invention, the preparation method of the maleic anhydride grafted polyethylene / mica sheet composite material includes: adding mica sheets into ethanol, adding 3-aminopropyltrimethoxysilane, ultrasonic treatment, drying to obtain modified mica sheets; dispersing the modified mica sheets in toluene, adding maleic anhydride grafted polyethylene, introducing nitrogen, reacting, after the reaction is completed, placing the reaction solution in methanol, filtering to collect the solid, and drying to obtain the maleic anhydride grafted polyethylene / mica sheet composite material.

[0010] A preferred embodiment of the present invention, adding mica sheets into ethanol, adding 3-aminopropyltrimethoxysilane, ultrasonic treatment at 30~40°C with a power of 50~100kHz for 2~5h, drying to obtain modified mica sheets; dispersing the modified mica sheets in toluene, adding maleic anhydride grafted polyethylene, introducing nitrogen, stirring and reacting at a temperature of 120~130°C for 2~3 hours, after the reaction is completed, placing the reaction solution in methanol, filtering to collect the solid, and drying to obtain the maleic anhydride grafted polyethylene / mica sheet composite material.

[0011] A preferred embodiment of the present invention, the preparation method of the polyolefin-coated modified nanoparticles includes: placing the monomers of polyolefin, modified nanoparticles, catalyst and solvent in a closed and dry reactor, carrying out a constant temperature polymerization reaction at 70~80°C for 4~8h, adding an ethanol solution of 3% HCl to terminate the polymerization, filtering, washing, and drying to obtain the polyolefin-coated modified nanoparticles.

[0012] A preferred embodiment of the present invention, the preparation method of the modified nanoparticles includes: adding nano calcium carbonate, nano titanium dioxide, nano silicon dioxide and sodium dodecyl sulfonate into deionized water, stirring and dispersing to obtain a mixed solution one; adding graphene oxide into ethanol, then adding hexamethyldisilazane and 3-aminopropyltriethoxysilane, mixing evenly to obtain a mixed solution two; mixing the mixed solution one and the mixed solution two, ultrasonic treatment, drying to obtain the modified nanoparticles.

[0013] A preferred embodiment of the present invention, the preparation method of the kaolin / modified nano alumina composite material includes: adding modified nano alumina into kaolin, mixing evenly and then placing it in a grinder for grinding for 1~3h to obtain a mixed material; placing the mixed material in a muffle furnace, roasting at 350~400°C for 3~5h, cooling to room temperature with the furnace, and grinding to obtain the kaolin / modified nano alumina composite material.

[0014] A preferred embodiment of the present invention, the preparation method of the modified nano alumina includes: dispersing nano alumina in water to form a dispersion; mixing vinyltriethoxysilane and ethanol evenly, adding the dispersion and mixing evenly, adjusting the pH to 6.5~7, stirring at a constant temperature of 60~70°C for 1~3h, cooling and drying to obtain the modified nano alumina.

[0015] A preferred embodiment of the present invention, the preparation method of the modified cyclodextrin / nanozinc oxide composite material comprises: adding β-cyclodextrin into water at a temperature of 60-70°C, then adding polyethylene glycol, stirring for 1-2 h, filtering to obtain a precipitate, drying to obtain modified cyclodextrin; mixing the modified cyclodextrin, nanozinc oxide and silane coupling agent KH550 evenly, drying to prepare the modified cyclodextrin / nanozinc oxide composite material.

[0016] A preferred embodiment of the present invention, the raw materials for preparing the inner layer include: 30-50 wt% metallocene high density polyethylene and 50-70 wt% metallocene medium density polyethylene.

[0017] A preferred embodiment of the present invention, the raw materials for preparing the outer layer include: 50-70 wt% metallocene high density polyethylene and 30-50 wt% metallocene medium density polyethylene.

[0018] A preparation method of a high-barrier polyethylene composite film, comprising the following steps:

[0019] S1. Mix metallocene high density polyethylene and metallocene medium density polyethylene, add them into an extruder to obtain an outer layer matrix and an inner layer matrix respectively; mix the maleic anhydride grafted polyethylene / mica sheet composite material, polyolefin-coated modified nanoparticles, kaolin / modified nanoaluminum oxide composite material and modified cyclodextrin / nanozinc oxide composite material evenly, add polyethylene and continue to mix evenly, finally add a crosslinking agent and mix evenly, add it into an extruder to extrude and pelletize to obtain a middle layer matrix;

[0020] S2. Put the outer layer matrix, the middle layer matrix and the inner layer matrix into a blow molding device, and co-extrude and blow mold to prepare the high-barrier polyethylene composite film.

[0021] The present invention has at least one of the following beneficial effects:

[0022] In the present invention, polyethylene is blended and pelletized with maleic anhydride grafted polyethylene / mica sheet composite material, polyolefin-coated modified nanoparticles, bentonite / modified nanoaluminum oxide composite material, modified cyclodextrin / nanozinc oxide composite material and a crosslinking agent to form a middle layer, and co-extrusion blown film is made with the inner layer and the outer layer formed by metallocene high density polyethylene and metallocene high density polyethylene to form a composite film, which can improve the mechanical strength and barrier properties of the composite film.

[0023] The maleic anhydride grafted polyethylene / mica flake composite of the present invention, the maleic anhydride grafted polyethylene not only has good processability and other excellent properties of polyethylene, but also has the re-reactivity and strong polarity of maleic anhydride polar molecules; the mica flake is in the shape of a thin sheet and has water barrier properties. The mica flake is dispersed in the inner layer of the polyethylene film, which can play a role in blocking water vapor from penetrating the polyethylene film. When the raw materials are melt-blended, the melting point of the mica flake has not been reached, so that the mica flake maintains a flaky structure, playing a role in blocking and improving the barrier performance of the polyethylene film; however, the dispersibility of the mica flake in polyethylene is not good. Therefore, the present invention forms a maleic anhydride grafted polyethylene / mica flake composite by combining maleic anhydride grafted polyethylene with mica flakes, improving the dispersion effect of the mica flakes, thereby helping to improve the barrier performance of the polyethylene film.

[0024] The modified nanoparticles of the present invention include nano calcium carbonate, nano titanium dioxide, nano silicon dioxide and graphene oxide. By modifying these nanoparticles, their dispersibility in polyethylene can be improved, and further polyolefin is used to coat these modified nanoparticles, enabling the nanoparticles to be uniformly dispersed in polyethylene; nano calcium carbonate, nano titanium dioxide, and nano silicon dioxide can improve the mechanical strength, aging resistance and temperature resistance of the polyethylene film, and graphene oxide can form a complex network structure, which can not only improve the mechanical strength of the polyethylene film, but also cooperate with mica flakes to improve the barrier performance of the polyethylene film.

[0025] The present invention modifies nano alumina, reduces the agglomeration of nano alumina, and disperses the modified nano alumina in bentonite to form a bentonite / modified nano alumina composite, which can make nano alumina fully dispersed in polyethylene, improving the mechanical strength and barrier performance of polyethylene. By modifying β-cyclodextrin, hydroxyl groups are further introduced, and nano zinc oxide is mixed with the modified cyclodextrin, which can not only improve the dispersibility of nano zinc oxide, but also β-cyclodextrin reacts with a cross-linking agent to wrap nano zinc oxide inside. This cross-linked β-cyclodextrin shell is tight and not easily damaged during the wrapping process, with higher stability, improving the mechanical strength and barrier performance of the polyethylene film; and the uniformly dispersed nano zinc oxide has better photocatalytic activity and antibacterial properties, endowing the film material with excellent antibacterial and mildew-proof effects, and expanding the development and application of polyethylene in packaging films and other aspects. Specific embodiments

[0026] The following uses specific examples to further illustrate the present invention in detail, but the present invention is not limited to the following specific examples. Example 1

[0027] A high-barrier polyethylene composite film is made by co-extrusion blow molding of three layers: an inner layer, a middle layer and an outer layer;

[0028] The raw materials for preparing the inner layer include: 30 wt% metallocene high-density polyethylene and 70 wt% metallocene medium-density polyethylene.

[0029] The raw materials for the middle layer include, by weight: 80 parts of low-density polyethylene, 10 parts of maleic anhydride grafted polyethylene / mica sheet composite, 10 parts of polyolefin-coated modified nanoparticles, 2 parts of kaolin / modified nano-aluminum oxide composite, 3 parts of modified cyclodextrin / nano-zinc oxide composite, and 0.1 part of MDI crosslinking agent.

[0030] The raw materials for the outer layer include: 50 wt% metallocene high-density polyethylene and 50 wt% metallocene medium-density polyethylene.

[0031] Among them, the preparation method of the maleic anhydride grafted polyethylene / mica sheet composite includes: adding 1 g of mica sheet to 10 mL of ethanol, adding 0.02 g of 3-aminopropyltrimethoxysilane, ultrasonic treating at 35 °C with a power of 80 kHz for 3 h, drying to obtain modified mica sheet; dispersing 1 g of modified mica sheet in 10 mL of toluene, adding 10 g of maleic anhydride grafted polyethylene, introducing nitrogen, stirring and reacting at 130 °C for 2 h, after the reaction is completed, placing the reaction solution in methanol, filtering and collecting the solid, and drying to obtain the maleic anhydride grafted polyethylene / mica sheet composite.

[0032] The polyolefin-coated modified nanoparticles in this embodiment are specifically polyethylene-coated modified nanoparticles, and the preparation method of the polyethylene-coated modified nanoparticles includes: placing 50 g of ethylene, 5 g of propylene, 2 g of modified nanoparticles, 0.1 g of catalyst, and 4 g of cyclohexane solvent in a closed and dry reactor, carrying out a constant temperature polymerization reaction at 70 °C for 6 h, adding an ethanol solution of 3% HCl to terminate the polymerization, filtering, washing, and drying to obtain the polyolefin-coated modified nanoparticles.

[0033] The preparation method of the modified nanoparticles includes: adding 1 g of nano-calcium carbonate, 1 g of nano-titanium dioxide, 1 g of nano-silica, and 0.03 g of sodium dodecylsulfonate to 10 mL of deionized water, stirring and dispersing to obtain a first mixed solution; adding 1 g of graphene oxide to 10 mL of ethanol, then adding 0.02 g of hexamethyldisilazane and 0.01 g of 3-aminopropyltriethoxysilane, mixing evenly to obtain a second mixed solution; mixing the first mixed solution and the second mixed solution, ultrasonic treating at a power of 50 kHz for 2 h, and drying to obtain the modified nanoparticles.

[0034] The preparation method of the kaolin / modified nano-aluminum oxide composite includes: adding 1 g of modified nano-aluminum oxide to 5 g of kaolin, mixing evenly and then placing it in a grinder to grind for 2 h to obtain a mixed material; placing the mixed material in a muffle furnace, roasting at 350 °C for 3 h, cooling to room temperature with the furnace, and then grinding to obtain the kaolin / modified nano-aluminum oxide composite.

[0035] The preparation method of the modified nano-aluminum oxide includes: dispersing 1 g of nano-aluminum oxide in 10 mL of water to form a dispersion; mixing 0.01 g of vinyltriethoxysilane with 5 mL of ethanol evenly, adding it to the dispersion and mixing evenly, adjusting the pH to 6.8, stirring at a constant temperature of 65 °C for 2 h, cooling and drying to obtain the modified nano-aluminum oxide.

[0036] The preparation method of the modified cyclodextrin / nano-zinc oxide composite material includes: adding 2 g of β-cyclodextrin to 20 mL of water at a temperature of 50 °C, then adding 4 g of polyethylene glycol, stirring for 1 h, filtering to obtain a precipitate, and drying to obtain the modified cyclodextrin; mixing 5 g of the modified cyclodextrin, 1 g of nano-zinc oxide and 0.01 g of silane coupling agent KH550 evenly, and drying to obtain the modified cyclodextrin / nano-zinc oxide composite material.

[0037] A preparation method of a high-barrier polyethylene composite film includes the following steps:

[0038] S1. Mix metallocene high-density polyethylene and metallocene medium-density polyethylene, add them into an extruder to obtain an outer matrix and an inner matrix respectively; mix the maleic anhydride-grafted polyethylene / mica sheet composite material, polyolefin-coated modified nanoparticles, kaolin / modified nano-aluminum oxide composite material and modified cyclodextrin / nano-zinc oxide composite material evenly, add polyethylene and continue to mix evenly, and finally add a cross-linking agent and mix evenly, then add it into an extruder to extrude and pelletize to obtain a middle matrix;

[0039] S2. Put the outer matrix, middle matrix and inner matrix into a blow molding device, and co-extrude and blow mold to obtain the high-barrier polyethylene composite film. Example 2

[0040] A high-barrier polyethylene composite film is made by co-extrusion blow molding of three layers, namely an inner layer, a middle layer and an outer layer;

[0041] The preparation raw materials of the inner layer include: 35 wt% of metallocene high-density polyethylene and 65 wt% of metallocene medium-density polyethylene.

[0042] The raw materials of the middle layer include, by weight: 90 parts of low-density polyethylene, 12 parts of maleic anhydride-grafted polyethylene / mica sheet composite material, 12 parts of polyolefin-coated modified nanoparticles, 3 parts of kaolin / modified nano-aluminum oxide composite material, 4 parts of modified cyclodextrin / nano-zinc oxide composite material, and 0.12 parts of MDI cross-linking agent.

[0043] The raw materials of the outer layer include: 55 wt% of metallocene high-density polyethylene and 45 wt% of metallocene medium-density polyethylene.

[0044] Among them, the preparation method of the maleic anhydride grafted polyethylene / mica sheet composite material includes: adding 1 g of mica sheets to 10 mL of ethanol, adding 0.02 g of 3-aminopropyltrimethoxysilane, treating with ultrasonic waves at a power of 80 kHz at 35 °C for 3 h, and drying to obtain modified mica sheets; dispersing 1 g of modified mica sheets in 10 mL of toluene, adding 10 g of maleic anhydride grafted polyethylene, introducing nitrogen, stirring and reacting at a temperature of 130 °C for 2 hours, after the reaction is completed, placing the reaction solution in methanol, filtering to collect the solid, and drying to obtain the maleic anhydride grafted polyethylene / mica sheet composite material.

[0045] The polyolefin-coated modified nanoparticles in this example are specifically polyethylene-coated modified nanoparticles. The preparation method of the polyethylene-coated modified nanoparticles includes: placing 50 g of ethylene, 5 g of propylene, 2 g of modified nanoparticles, 0.1 g of catalyst, and 4 g of cyclohexane solvent in a sealed and dry reactor, carrying out a constant-temperature polymerization reaction at 70 °C for 6 h, adding an ethanol solution of 3% HCl to terminate the polymerization, filtering, washing, and drying to obtain the polyolefin-coated modified nanoparticles.

[0046] The preparation method of the modified nanoparticles includes: adding 1 g of nano calcium carbonate, 1 g of nano titanium dioxide, 1 g of nano silicon dioxide, and 0.03 g of sodium dodecyl sulfonate to 10 mL of deionized water, stirring and dispersing to obtain a mixed solution one; adding 1 g of graphene oxide to 10 mL of ethanol, then adding 0.02 g of hexamethyldisilazane and 0.01 g of 3-aminopropyltriethoxysilane, and mixing evenly to obtain a mixed solution two; mixing the mixed solution one and the mixed solution two, treating with ultrasonic waves at a power of 50 kHz for 2 h, and drying to obtain the modified nanoparticles.

[0047] The preparation method of the kaolin / modified nanoaluminum oxide composite material includes: adding 1 g of modified nanoaluminum oxide to 5 g of kaolin, mixing evenly and then placing it in a grinder for grinding for 2 h to obtain a mixed material; placing the mixed material in a muffle furnace, roasting at 350 °C for 3 h, cooling to room temperature with the furnace, and then grinding to obtain the kaolin / modified nanoaluminum oxide composite material.

[0048] The preparation method of the modified nanoaluminum oxide includes: dispersing 1 g of nanoaluminum oxide in 10 mL of water to form a dispersion; mixing 0.01 g of vinyltriethoxysilane with 5 mL of ethanol evenly, adding it to the dispersion and mixing evenly, adjusting the pH to 6.8, stirring at a constant temperature of 65 °C for 2 h, cooling and drying to prepare the modified nanoaluminum oxide.

[0049] The preparation method of the modified cyclodextrin / nano-zinc oxide composite material comprises: adding 2 g of β-cyclodextrin into 20 mL of water at 50 °C, then adding 4 g of polyethylene glycol, stirring for 1 h, filtering to obtain a precipitate, and drying to obtain the modified cyclodextrin; mixing 5 g of the modified cyclodextrin, 1 g of nano-zinc oxide and 0.01 g of silane coupling agent KH550 evenly, and drying to prepare the modified cyclodextrin / nano-zinc oxide composite material.

[0050] A preparation method of a high-barrier polyethylene composite film comprises the following steps:

[0051] S1. Mix metallocene high-density polyethylene and metallocene medium-density polyethylene, and add them into an extruder to obtain an outer matrix and an inner matrix respectively; mix the maleic anhydride grafted polyethylene / mica sheet composite material, polyolefin-coated modified nanoparticles, kaolin / modified nano-aluminum oxide composite material and modified cyclodextrin / nano-zinc oxide composite material evenly, add polyethylene and continue to mix evenly, finally add a crosslinking agent and mix evenly, and add them into an extruder to extrude and pelletize to obtain a middle matrix;

[0052] S2. Put the outer matrix, the middle matrix and the inner matrix into a blow molding device, and co-extrude and blow mold to prepare the high-barrier polyethylene composite film. Example 3

[0053] A high-barrier polyethylene composite film is made by co-extrusion blown film of three layers including an inner layer, a middle layer and an outer layer;

[0054] The preparation raw materials of the inner layer include: 40 wt% of metallocene high-density polyethylene and 60 wt% of metallocene medium-density polyethylene.

[0055] The raw materials of the middle layer include, by weight: 100 parts of low-density polyethylene, 15 parts of maleic anhydride grafted polyethylene / mica sheet composite material, 15 parts of polyolefin-coated modified nanoparticles, 4 parts of kaolin / modified nano-aluminum oxide composite material, 5 parts of modified cyclodextrin / nano-zinc oxide composite material, and 0.15 part of MDI crosslinking agent.

[0056] The raw materials of the outer layer include: 60 wt% of metallocene high-density polyethylene and 40 wt% of metallocene medium-density polyethylene.

[0057] Among them, the preparation method of the maleic anhydride grafted polyethylene / mica sheet composite material includes: adding 1 g of mica sheets into 10 mL of ethanol, adding 0.02 g of 3-aminopropyltrimethoxysilane, subjecting to ultrasonic treatment at a power of 80 kHz at 35 °C for 3 h, and drying to obtain modified mica sheets; dispersing 1 g of modified mica sheets in 10 mL of toluene, adding 10 g of maleic anhydride grafted polyethylene, introducing nitrogen, stirring and reacting at a temperature of 130 °C for 2 hours, after the reaction is completed, placing the reaction solution in methanol, filtering and collecting the solid, and drying to obtain the maleic anhydride grafted polyethylene / mica sheet composite material.

[0058] The polyolefin-coated modified nanoparticles in this example are specifically polyethylene-coated modified nanoparticles, and the preparation method of the polyethylene-coated modified nanoparticles includes: placing 50 g of ethylene, 5 g of propylene, 2 g of modified nanoparticles, 0.1 g of catalyst and 4 g of cyclohexane solvent in a closed and dry reactor, carrying out a constant temperature polymerization reaction at 70 °C for 6 h, adding an ethanol solution of 3% HCl to terminate the polymerization, filtering, washing, and drying to obtain the polyolefin-coated modified nanoparticles.

[0059] The preparation method of the modified nanoparticles includes: adding 1 g of nano calcium carbonate, 1 g of nano titanium dioxide, 1 g of nano silicon dioxide and 0.03 g of sodium dodecyl sulfonate into 10 mL of deionized water, stirring and dispersing to obtain a first mixed solution; adding 1 g of graphene oxide into 10 mL of ethanol, then adding 0.02 g of hexamethyldisilazane and 0.01 g of 3-aminopropyltriethoxysilane, mixing evenly to obtain a second mixed solution; mixing the first mixed solution and the second mixed solution, subjecting to ultrasonic treatment at a power of 50 kHz for 2 h, and drying to obtain the modified nanoparticles.

[0060] The preparation method of the kaolin / modified nano alumina composite material includes: adding 1 g of modified nano alumina into 5 g of kaolin, mixing evenly and then placing in a grinder for grinding for 2 h to obtain a mixed material; placing the mixed material in a muffle furnace, roasting at 350 °C for 3 h, cooling to room temperature with the furnace, and grinding to obtain the kaolin / modified nano alumina composite material.

[0061] The preparation method of the modified nano alumina includes: dispersing 1 g of nano alumina in 10 mL of water to form a dispersion; mixing 0.01 g of vinyltriethoxysilane with 5 mL of ethanol evenly, adding the dispersion and mixing evenly, adjusting the pH to 6.8, stirring at a constant temperature of 65 °C for 2 h, cooling and drying to prepare the modified nano alumina.

[0062] The preparation method of the modified cyclodextrin / nano-zinc oxide composite material comprises: adding 2 g of β-cyclodextrin into 20 mL of water at 50 °C, then adding 4 g of polyethylene glycol, stirring for 1 h, filtering to obtain a precipitate, and drying to obtain the modified cyclodextrin; mixing 5 g of the modified cyclodextrin, 1 g of nano-zinc oxide and 0.01 g of silane coupling agent KH550 evenly, and drying to prepare the modified cyclodextrin / nano-zinc oxide composite material.

[0063] A preparation method of a high-barrier polyethylene composite film comprises the following steps:

[0064] S1. Mixing metallocene high-density polyethylene and metallocene medium-density polyethylene, and adding them into an extruder to respectively obtain an outer matrix and an inner matrix; mixing the maleic anhydride grafted polyethylene / mica sheet composite material, the polyolefin-coated modified nanoparticles, the kaolin / modified nano-aluminum oxide composite material and the modified cyclodextrin / nano-zinc oxide composite material evenly, adding polyethylene and continuing to mix evenly, finally adding a crosslinking agent and mixing evenly, and adding them into an extruder to extrude and pelletize to obtain a middle matrix;

[0065] S2. Putting the outer matrix, the middle matrix and the inner matrix into a blow molding device, and co-extruding and blow molding to prepare the high-barrier polyethylene composite film. Example 4

[0066] A high-barrier polyethylene composite film is made by co-extrusion blow molding of three layers, namely an inner layer, a middle layer and an outer layer;

[0067] The preparation raw materials of the inner layer include: 45 wt% of metallocene high-density polyethylene and 55 wt% of metallocene medium-density polyethylene.

[0068] The raw materials of the middle layer include, by weight: 110 parts of low-density polyethylene, 18 parts of maleic anhydride grafted polyethylene / mica sheet composite material, 18 parts of polyolefin-coated modified nanoparticles, 5 parts of kaolin / modified nano-aluminum oxide composite material, 6 parts of modified cyclodextrin / nano-zinc oxide composite material, and 0.18 part of MDI crosslinking agent.

[0069] The raw materials of the outer layer include: 65 wt% of metallocene high-density polyethylene and 35 wt% of metallocene medium-density polyethylene.

[0070] Among them, the preparation method of the maleic anhydride grafted polyethylene / mica sheet composite material includes: adding 1 g of mica sheets to 10 mL of ethanol, adding 0.02 g of 3-aminopropyltrimethoxysilane, and performing ultrasonic treatment at a power of 80 kHz at 35 °C for 3 h, followed by drying to obtain modified mica sheets; dispersing 1 g of the modified mica sheets in 10 mL of toluene, adding 10 g of maleic anhydride grafted polyethylene, introducing nitrogen, and stirring and reacting at a temperature of 130 °C for 2 hours. After the reaction is completed, the reaction solution is placed in methanol, and the solid is collected by filtration and dried to obtain the maleic anhydride grafted polyethylene / mica sheet composite material.

[0071] The polyolefin-coated modified nanoparticles in this example are specifically polyethylene-coated modified nanoparticles. The preparation method of the polyethylene-coated modified nanoparticles includes: placing 50 g of ethylene, 5 g of propylene, 2 g of modified nanoparticles, 0.1 g of catalyst, and 4 g of cyclohexane solvent in a closed and dry reactor, carrying out a constant-temperature polymerization reaction at 70 °C for 6 h, adding an ethanol solution of 3% HCl to terminate the polymerization, filtering, washing, and drying to obtain the polyolefin-coated modified nanoparticles.

[0072] The preparation method of the modified nanoparticles includes: adding 1 g of nano calcium carbonate, 1 g of nano titanium dioxide, 1 g of nano silicon dioxide, and 0.03 g of sodium dodecyl sulfonate to 10 mL of deionized water, stirring and dispersing to obtain a mixed solution I; adding 1 g of graphene oxide to 10 mL of ethanol, then adding 0.02 g of hexamethyldisilazane and 0.01 g of 3-aminopropyltriethoxysilane, and mixing evenly to obtain a mixed solution II; mixing the mixed solution I and the mixed solution II, performing ultrasonic treatment at a power of 50 kHz for 2 h, and drying to obtain the modified nanoparticles.

[0073] The preparation method of the kaolin / modified nano-aluminum oxide composite material includes: adding 1 g of modified nano-aluminum oxide to 5 g of kaolin, mixing evenly and then placing it in a grinder for grinding for 2 h to obtain a mixed material; placing the mixed material in a muffle furnace, roasting at 350 °C for 3 h, cooling to room temperature with the furnace, and then grinding to obtain the kaolin / modified nano-aluminum oxide composite material.

[0074] The preparation method of the modified nano-aluminum oxide includes: dispersing 1 g of nano-aluminum oxide in 10 mL of water to form a dispersion; mixing 0.01 g of vinyltriethoxysilane with 5 mL of ethanol evenly, adding it to the dispersion and mixing evenly, adjusting the pH to 7, stirring at a constant temperature of 65 °C for 2 h, cooling and drying to obtain the modified nano-aluminum oxide.

[0075] The preparation method of the modified cyclodextrin / nano-zinc oxide composite material comprises: adding 2 g of β-cyclodextrin into 20 mL of water at 50 °C, then adding 4 g of polyethylene glycol, stirring for 1 h, filtering to obtain a precipitate, and drying to obtain the modified cyclodextrin; mixing 5 g of the modified cyclodextrin, 1 g of nano-zinc oxide and 0.01 g of silane coupling agent KH550 evenly, and drying to prepare the modified cyclodextrin / nano-zinc oxide composite material.

[0076] A preparation method of a high-barrier polyethylene composite film comprises the following steps:

[0077] S1. Mix metallocene high-density polyethylene and metallocene medium-density polyethylene, and add them into an extruder to obtain an outer matrix and an inner matrix respectively; mix the maleic anhydride grafted polyethylene / mica sheet composite material, the polyolefin-coated modified nanoparticles, the kaolin / modified nano-aluminum oxide composite material and the modified cyclodextrin / nano-zinc oxide composite material evenly, add polyethylene and continue to mix evenly, and finally add a crosslinking agent and mix evenly, and add them into an extruder to extrude and pelletize to obtain a middle matrix;

[0078] S2. Put the outer matrix, the middle matrix and the inner matrix into a blow molding device, and co-extrude and blow mold to prepare the high-barrier polyethylene composite film. Example 5

[0079] A high-barrier polyethylene composite film is made by co-extrusion blow molding of three layers, namely an inner layer, a middle layer and an outer layer;

[0080] The preparation raw materials of the inner layer include: 50 wt% of metallocene high-density polyethylene and 50 wt% of metallocene medium-density polyethylene.

[0081] The raw materials of the middle layer include, by weight: 120 parts of low-density polyethylene, 20 parts of maleic anhydride grafted polyethylene / mica sheet composite material, 20 parts of polyolefin-coated modified nanoparticles, 6 parts of kaolin / modified nano-aluminum oxide composite material, 7 parts of modified cyclodextrin / nano-zinc oxide composite material, and 0.2 part of MDI crosslinking agent.

[0082] The raw materials of the outer layer include: 70 wt% of metallocene high-density polyethylene and 30 wt% of metallocene medium-density polyethylene.

[0083] Among them, the preparation method of the maleic anhydride grafted polyethylene / mica flake composite material includes: adding 1 g of mica flakes to 10 mL of ethanol, adding 0.02 g of 3-aminopropyltrimethoxysilane, and performing ultrasonic treatment at 35 °C with a power of 80 kHz for 3 h, followed by drying to obtain modified mica flakes; dispersing 1 g of the modified mica flakes in 10 mL of toluene, adding 10 g of maleic anhydride grafted polyethylene, introducing nitrogen, and stirring and reacting at a temperature of 130 °C for 2 hours. After the reaction is completed, placing the reaction solution in methanol, filtering to collect the solid, and drying to obtain the maleic anhydride grafted polyethylene / mica flake composite material.

[0084] The polyolefin-coated modified nanoparticles in this example are specifically polyethylene-coated modified nanoparticles. The preparation method of the polyethylene-coated modified nanoparticles includes: placing 50 g of ethylene, 5 g of propylene, 2 g of modified nanoparticles, 0.1 g of catalyst, and 4 g of cyclohexane solvent in a closed and dry reactor, carrying out a constant-temperature polymerization reaction at 70 °C for 6 h, adding an ethanol solution of 3% HCl to terminate the polymerization, filtering, washing, and drying to obtain the polyolefin-coated modified nanoparticles.

[0085] The preparation method of the modified nanoparticles includes: adding 1 g of nano calcium carbonate, 1 g of nano titanium dioxide, 1 g of nano silicon dioxide, and 0.03 g of sodium dodecyl sulfonate to 10 mL of deionized water, stirring and dispersing to obtain a first mixed solution; adding 1 g of graphene oxide to 10 mL of ethanol, then adding 0.02 g of hexamethyldisilazane and 0.01 g of 3-aminopropyltriethoxysilane, and mixing evenly to obtain a second mixed solution; mixing the first mixed solution and the second mixed solution, performing ultrasonic treatment at a power of 50 kHz for 2 h, and drying to obtain the modified nanoparticles.

[0086] The preparation method of the kaolin / modified nano alumina composite material includes: adding 1 g of modified nano alumina to 5 g of kaolin, mixing evenly and then placing it in a grinder for grinding for 2 h to obtain a mixed material; placing the mixed material in a muffle furnace, roasting at 350 °C for 3 h, cooling to room temperature with the furnace, and then grinding to obtain the kaolin / modified nano alumina composite material.

[0087] The preparation method of the modified nano alumina includes: dispersing 1 g of nano alumina in 10 mL of water to form a dispersion; mixing 0.01 g of vinyltriethoxysilane with 5 mL of ethanol evenly, adding it to the dispersion and mixing evenly, adjusting the pH to 6.5, stirring at a constant temperature of 65 °C for 2 h, cooling and drying to obtain the modified nano alumina.

[0088] The preparation method of the modified cyclodextrin / nano-zinc oxide composite material comprises: adding 2 g of β-cyclodextrin into 20 mL of water at 50 °C, then adding 4 g of polyethylene glycol, stirring for 1 h, filtering to obtain a precipitate, and drying to obtain the modified cyclodextrin; mixing 5 g of the modified cyclodextrin, 1 g of nano-zinc oxide and 0.01 g of silane coupling agent KH550 evenly, and drying to prepare the modified cyclodextrin / nano-zinc oxide composite material.

[0089] A preparation method of a high-barrier polyethylene composite film comprises the following steps:

[0090] S1. Mix metallocene high-density polyethylene and metallocene medium-density polyethylene, and add them into an extruder to obtain an outer matrix and an inner matrix respectively; mix the maleic anhydride grafted polyethylene / mica sheet composite material, polyolefin-coated modified nanoparticles, kaolin / modified nano-aluminum oxide composite material and modified cyclodextrin / nano-zinc oxide composite material evenly, add polyethylene and continue to mix evenly, and finally add a cross-linking agent and mix evenly, then add them into an extruder to extrude and pelletize to obtain a middle matrix;

[0091] S2. Put the outer matrix, the middle matrix and the inner matrix into a blow molding device, and co-extrude and blow mold to prepare the high-barrier polyethylene composite film. Comparative Example 1

[0092] The difference from Example 1 is that: the preparation raw materials of the middle layer do not include "maleic anhydride grafted polyethylene / mica sheet composite material, modified cyclodextrin / nano-zinc oxide composite material", and the others are the same as in Example 1. Comparative Example 2

[0093] The difference from Example 1 is that: the preparation raw materials of the middle layer do not include "polyolefin-coated modified nanoparticles, kaolin / modified nano-aluminum oxide composite material", and the others are the same as in Example 1.

[0094] Result test

[0095] Use a WDW100 type universal testing machine to measure the tensile strength and elongation at break of the high-barrier polyethylene composite films obtained in Examples 1-5 and Comparative Examples 1-2.

[0096] Measure the water vapor transmission rate of the high-barrier polyethylene composite films obtained in Examples 1-5 and Comparative Examples 1-2 according to the method specified in GB / T 21529-2008.

[0097] Measure the oxygen transmission rate of the high-barrier polyethylene composite films obtained in Examples 1-5 and Comparative Examples 1-2 according to the method specified in GB / T10004-2008.

[0098] The results are shown in Table 1: Table 1

[0099] Tensile strength (MPa) Elongation at break (%) <![CDATA[Water vapor transmission rate (g / m 2 ·24h)]]> <![CDATA[Oxygen transmission rate (cm 3 / m 2 / 24 h / Pa)]]> Example 1 17.6 898.4 1.94 681 Example 2 18.3 937.5 1.73 625 Example 3 18.8 990.2 1.68 573 Example 4 19.2 997.4 1.53 428 Example 5 18.1 979.4 1.59 415 Comparative Example 1 9.9 736.5 7.62 1930 Comparative Example 2 14.5 817.8 6.85 1665

[0100] As can be seen from Table 1, the high-barrier polyethylene composite films prepared in Examples 1 to 5 have good tensile strength and elongation at break, indicating that the high-barrier polyethylene composite films prepared in Examples 1 to 5 have good mechanical strength and high-barrier properties.

[0101] Comparing Examples 1 to 5 with Comparative Examples 1 to 2, it can be seen that the tensile strength and elongation at break of the high-barrier polyethylene composite films prepared in Examples 1 to 5 are significantly better than those of Comparative Example 1 (the preparation raw materials of the middle layer do not include maleic anhydride grafted polyethylene / mica sheet composite material and modified cyclodextrin / nano-zinc oxide composite material) and Comparative Example 2 (the preparation raw materials of the middle layer do not include polyolefin-coated modified nanoparticles and kaolin / modified nano-aluminum oxide composite material). This shows that by blending polyethylene with maleic anhydride grafted polyethylene / mica sheet composite material, polyolefin-coated modified nanoparticles, kaolin / modified nano-aluminum oxide composite material, modified cyclodextrin / nano-zinc oxide composite material and cross-linking agent to form pellets for the middle layer, and co-extrusion blowing with the inner and outer layers formed by metallocene high-density polyethylene and metallocene high-density polyethylene to make a composite film, the mechanical strength and barrier properties of the composite film can be improved.

[0102] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, shall be covered by the protection scope of the present invention.

Claims

1. A high-barrier polyethylene composite film, characterized in that, It is made by co-extrusion blown film of an inner layer, a middle layer and an outer layer; The raw materials for preparing the inner layer include: 30-50 wt% metallocene high density polyethylene and 50-70 wt% metallocene medium density polyethylene; The raw materials of the middle layer by weight include: 80-120 parts of polyethylene, 10-20 parts of maleic anhydride grafted polyethylene / mica sheet composite material, 10-20 parts of polyolefin-coated modified nanoparticles, 2-6 parts of kaolin / modified nano-aluminum oxide composite material, 3-7 parts of modified cyclodextrin / nano-zinc oxide composite material, and 0.1-0.2 parts of crosslinking agent; The raw materials for preparing the outer layer include: 50-70 wt% metallocene high density polyethylene and 30-50 wt% metallocene medium density polyethylene; The preparation method of the maleic anhydride grafted polyethylene / mica sheet composite material includes: adding mica sheets into ethanol, adding 3-aminopropyltrimethoxysilane, performing ultrasonic treatment at 30-40 °C with a power of 50-100 kHz for 2-5 h, drying to obtain modified mica sheets; dispersing the modified mica sheets in toluene, adding maleic anhydride grafted polyethylene, introducing nitrogen, stirring and reacting at a temperature of 120-130 °C for 2-3 hours, after the reaction is completed, placing the reaction solution in methanol, filtering to collect the solid, and drying to obtain the maleic anhydride grafted polyethylene / mica sheet composite material; The preparation method of the polyolefin-coated modified nanoparticles includes: placing the monomer of polyolefin, modified nanoparticles, catalyst and solvent in a closed and dry reactor, carrying out a constant temperature polymerization reaction at 70-80 °C for 4-8 h, adding an ethanol solution of 3% HCl to terminate the polymerization, filtering, washing, and drying to obtain polyolefin-coated modified nanoparticles; The preparation method of the modified nanoparticles includes: adding nano calcium carbonate, nano titanium dioxide, nano silicon dioxide and sodium dodecyl sulfonate into deionized water, stirring and dispersing to obtain a first mixed solution; adding graphene oxide into ethanol, then adding hexamethyldisilazane and 3-aminopropyltriethoxysilane, mixing evenly to obtain a second mixed solution; mixing the first mixed solution and the second mixed solution, carrying out ultrasonic treatment, and drying to obtain modified nanoparticles; The preparation method of the modified cyclodextrin / nano-zinc oxide composite material includes: adding β-cyclodextrin into water at a temperature of 60-70 °C, then adding polyethylene glycol, stirring for 1-2 h, filtering to obtain a precipitate, and drying to obtain modified cyclodextrin; mixing the modified cyclodextrin, nano-zinc oxide and silane coupling agent evenly, and drying to prepare the modified cyclodextrin / nano-zinc oxide composite material.

2. The high-barrier polyethylene composite film according to claim 1, wherein The preparation method of the kaolin / modified nano-aluminum oxide composite material includes: adding the modified nano-aluminum oxide into kaolin, mixing evenly and then placing it in a grinder for grinding for 1-3 h to obtain a mixed material; placing the mixed material in a muffle furnace, roasting at 350-400 °C for 3-5 h, cooling to room temperature with the furnace, and grinding to obtain the kaolin / modified nano-aluminum oxide composite material.

3. The high-barrier polyethylene composite film according to claim 1, wherein The preparation method of the modified nano-aluminum oxide comprises: dispersing nano-aluminum oxide in water to form a dispersion; mixing vinyltriethoxysilane and ethanol uniformly, adding the dispersion and mixing uniformly, adjusting the pH to 6.5 - 7, stirring at a constant temperature of 60 - 70 °C for 1 - 3 h, cooling and drying to obtain the modified nano-aluminum oxide.

4. A method for preparing a high-barrier polyethylene composite film according to any one of claims 1 to 3, characterized in that, It includes the following steps: S1. Mix metallocene high-density polyethylene and metallocene medium-density polyethylene, and add them into an extruder to obtain an outer matrix and an inner matrix respectively; mix the maleic anhydride grafted polyethylene / mica sheet composite material, polyolefin-coated modified nanoparticles, kaolin / modified nano-aluminum oxide composite material and modified cyclodextrin / nano-zinc oxide composite material uniformly, add polyethylene and continue to mix uniformly, finally add a cross-linking agent and mix uniformly, and add it into an extruder to extrude and pelletize to obtain a middle matrix. S2. Put the outer matrix, the middle matrix and the inner matrix into a blow molding device, and co-extrude and blow mold to obtain a high-barrier polyethylene composite film.